Indophenol intermediate and blue sulphur dye derived therefrom



9 dium sulfide bath.

. No Drawing.

Patented Oct. 7,1930

UNIT D STATES WALTER ncmnivss, or vwimvrnxrcr'ron,--nnnhiwvnnE, assrernon T no PONT ma .NEMOURS & COMPANY, or wrnmmeron, DELAWARE, A conroan'rron or nnnn- WARE.

mmmmr. INTERMEDIATE am) sm qnrnmmzs mvsp v, i

This inyention relatesto a methodof pre' paring a sulphur blue dye and comprises preparmg an indophenol at a temperature indophenol; p t p t p It is Well known in the art that an .in-

below 0 (1:, andsubsequently thionatingthe dophenol is produced by condensing p nitrosophenol with diphenylamine in a sulphuric MIG acid medium. According to the usual method the diphenylamine is dissolved.in75% sulphuricacid andtthe solution cooled to about l C. and to this isadded the solution of pnitrosophenol in 75% acid so that the'teme perature does not rise abQveabout j'O;-

The indophenol, solution is then poured into iceliwater and the precipitated indoph nol is filtered off and washed With Waterto free it fromexcess acid. Theindophenol soobtained is quite impure and contains ajlarge proportion of icy-products which interfere materially in the preparation of the sulphur blue dyes by thionation offthe indophenol.

strength.

Because of the contained impurities;- is the Another of the objects of myyinyentionis the manufacture, of. dyes from these pureindophenols bya method especially ad'vanta-j geous for these particularlcompounds, in that the yield and quality of the dyes are vgreatly improved. The purity of theindophenolis.

Lrefiected in'the quality of sulphur dye'tvhich, when derived from it by the present method, is practically completely soluble in the so The characteristic features of my newin dophenolprocess are in the low condensation temperature employed, ia, about 2 and in the time. consumed in the condensacrease the time requiredfor the condensa- Application fiia October 27, [1925.1 Serial No. 65,242; e

ployed permits of a'reactionat alqw. initial temperature of about 20 CQto which one of the component solutions is cooled. Accordingltof the method of carryingout the condensation, the greater part'of the reac- :tion takes place lattemperatures substantially below 82 C3 To revent decomposition during .the precipitation and subsequent treatmentof theindophenol, speed isrequired i i in freeing the product from tlieiacid. Fi;

nally, it has been found advantageous tocom 3 pletely'remove all adhering acid by neutralize ing' the indophenol pasteiwith a dilute allta' line solution or to form the stable leucjo in-v dophenol by treating the acid indophenol paste wfith sodium sulfide inj a neutral :;or.

slightly acidsolution. F

All i dophenolptowhich myfttionautny i process is] particularly applicableimay prepared,*for 'exampleas followsz t t Oneypartiof diphenylamine is dissolvedin 3.2 parts ofj93 sulphuificacid at "4:0 5 O C andcooledtoabout C. At the same time 0.755 part ofpnitrosophenolis dissolved in 12 ,55 part s'o f 6 t% sulphuric acidat about I 0 C and cooled to 20C.; Thediphenyljamine solution is then irunintoi the 'nitrosophenol solution as rapidly as possible "at. a

temperature belowl) C. eztternal cooling heing required during the addition. The indophenollsolution is then-stirred for about 10. minutes andis'runvinto Topartsof a mix- :dried at. ab0utq50L O1 When tested for puritytthe indophenol is completely soluble inethyllalcohol and alsoin. an alcoholiepolysulfide so'lution .I, M i Technically, it is yoften l. advantageous to isolate: the: indophenol in "the more stable leuco 1 iorm. To accomplish" this, the acid press cake is treat'ed with sodium sulfide in a neutral {'or' slightly acid solution, in place of the neutralization with the sodaash solu- -tion treatmentfi The leuco-indophenol is then filtered, thoroughly washed and dried at about 50 C.

The above mentioned amounts of materials and strengths of acid can, of course, be varied within certain limits. Since the sulphuric acid used in this process is a condensing medium which serves to dissolve the initial intermediates and to-absorb the water formed in the reaction, the amount of acid employed can be varied considerably without afiecting the product. The lower limitprobably' would be" dependent only upon the amount of acid necessary for dissolving the initial materials. The upper limit to the amount used can be extended indefinitely but,

of course, itwould be economically unwise to use more than is absolutely necessary to maintain the proper solution and necessary regulation of temperature. The initial strength ofthe acid employed prior to any reaction taking place could be conveniently varied from about to 71%. If desired, the amount of p-nitrosophenol can be increased from 3 to 5%, suitable changes being made in the amount of diphenylamine used. The amount of soda ash can be increased 100% or more if desired.

Several methods have been suggested for converting indophenol or leuco indophenol into dyes. One method for producing the color is that in which the indophenolic bodies are heated with an alcoholic sodium tetrasulfide solution under high pressures. Another process is that which consists of heating the indophenol with a solution of sodium pentasulfide in alcohol under reflux. To obtain the color, the alcohol is distilled air, the residue is dissolved in water, and after filtra tion the dye is precipitated from the filtrate by oxidation. The dyes made by the usual processes, however, are generally unsuitable for use on the various types of dyeing machines without the use of some purification process.

By carrying out the preparation of the indophenol according to the process described above, and by thionating and purifying the dye according to my improved process, as described below, the yield and quality of the resulting dye are markedly improved. This dye. prepared according to my process, is characterizedby being a more completely thionated product, and by being practically free from the partially thionated indophenol, which constituent is of redder shade and of poorer strength. In order to completely thionate the indophenol, it may be mixed with sodium sulphide, alcohol and sulphur, and the mixture boiled, using high steam pressures in the heating element and very efficient agitation. It is also advantageous to use a large excess of a polysulfide containing a high percentage of sulphur, for example, Na S I Toj render the dye practically. free from partially thionated indophenolic constituents, a suflicient quantity of an alkalme hydroxide is added to the melt prior to the distillation of the alcohol to reduce the polysulfide to a trior tetra-sulfide in which solution the more highly thionated product is insoluble and from which it can be filtered oil.

It has been found that this dye possesses the property of losing tinctorial strength and of decomposing to form a material which is insoluble in dilute sodium sulfide, upon dry-- ing or upon longstanding. By making the purified dye paste slightly acid by the addi: tion of a weak acid and a solution of a salt having acidic properties, such assodium bisulfate, these harmful properties can be corrected. I y

The following is a convenient and preferred process for preparing the sulphur blue dye from the indophenol:

One part of the above mentioned indophenol or leuco-indophenol is added to a solution of 2.85 parts of fused sodium sulfide and 4.5 parts of sulphur in 7.5 parts of alcohol. The mixture is boiled vigorously in a suitable kettle with a jacket temperature of 135-l45 C. and with very elficient stirring until the thionation is complete, the time required being from 90 to 180 hours. A solution of 0.9 part of caustic soda in 3.5 partsiof water is added and, after the alcohol. is distilled off, the dye mixture is diluted further and filtered. The dye paste is first washed with a dilute salt solution and ,later with water. It is then neutralized with a 20% solution of sulphuric acid and treated with 0.1 part of sodium bisulfate.

The amounts of materials used can be Va ried withincertain limits depending upon the conditions of operation. The tempera tures and time may suitably be varied to conform with the product desired.

Any suitable salt having acidic properties may be used in place of the'sodium bisulfate.

As a criterion of purity and quality, a dyeing shows this colorv to be considerably greener and brighter, and much stronger than any commercial product made from those intermediates. This sulphur blue dye is practically completely soluble in dilute sodium sulfide solution of such strength as is used in dyeing. If a little sodium hydrosulfite is added to this solution, a clear light yellow vat dye is obtained. This new dye also can be used on the various types of dyeing machines without further purification.

I claim:

1. The process of making a blue sulphur dye which comprises forming an indophenol from p-nitrosophenol and diphenyl amine by condensation at a temperaturebelow 0 C. and thionating the indophenol. so formed.

2. The process of making a blue sulphur dye, which comprises forming an indophenol from p-nitrosophenol and diphenylamine 3 4 by condensation atfa temperature below (1., .thionating the indophenol and treating the thionated product with caustic alkali.-

3. The process of making a blue sulphur .dye from an indophenol obtained by con (lensing p-nitrosophenol and diphenylamine.

at a temperature below 0 C. which comprises boiling a mixture of said indophenol,

alcohol, a soluble polysulfide and sulphur,

addingcaustic alkali to the boiled mixture,

separating and washing the dye. V

4.)The process of making a blue sulphur,

dye which comprises forming an indophenol from p nitrosophenol and diphenlyamine by condensation at a temperature. below 0 (1.,

thionatingthe indophenol so formed, treatingthethionated product with caustic alkali,

filtering, and acidifying the alkaline filter cake. e i v.

5 The process of making a blue sulphur dye from an indophen'ol obtained by the con densation of diphenylamine and p nitroi sophenol at a temperature below 0 (l which comprises, boiling a mixture of the indophe nol, alcohol and a soluble sulfide containing a high percentage of sulphur, adding 'caustic alkali to theboiled mixture," distilling off the alcohol, diluting the residuewitlijwater,

filtering elf the dye and washing the dye.

n01, alcohol, sodium sulfide and sulphur,

6. The process of making ablue sulphur dye from an indophenol obtained bythe condensation of diphenylamine and p -nitrosophenol at a temperature below 0 C. which comprises boiling a mixture ofthe indopheadding caustic alkali to the boiled mixture,

. distilling off the alcohol, diluting the residue,

i i filtering oif the dye, washing. the'dye, slightly acidifying the purified dye paste and treating the acid paste with asalt having acidic properties.

and yieldinga clearlight yellow yat upon in treatment with sodium. hydrosulfite.

10. In a process ofmaking a blue sulphur dye from inclophenol, the step which comprises condensing p-nitrosophenol and di-' phenylamine, the condensation being carried out at a temperature below 0 C,

11. In a process of making a blue sulphur dye from indophenol, by condensationthe step which comprises mixing, in the presence Of sulphuric acid, diphenylamine at a temperature ofabout C. with p-nitrosophenolat a temperature of about "20 1? and maintaining the mixture at a temperature.

' below 0 C. i y 7 12.. In a process of making a blue sulphur dye from indophenol, the step which comprises condensing diphenylamine withp-ni- 1 trosophenol at a temperature below 0 (1, drowning the condensation product in water at a temperature belou 5' O. to form a precipitate, and filtering, washing and neutralizing the precipitate. I r

1 3. In a process of making a blue sulphur dye from indophenol, the step which coIn- 7. A sulphur blue dye suitable 'formachine dyeing, obtainableby treating a thionated indophenol, said indophenol being formed by the condensation ofp-nitrosophenol and diphenylamine below 0 0., with caustic. alkali andwater to precipitate the dye,said

dye being completely soluble in sodium sulfide solutions. 7 V I 8. A blue sulphur dye suitable for machine dyeing, obtainable by treating a thionated indophenol, said indophenol being formedby the condensation of p-nitrosophenol and diphenylamine below 0 (1., with caustic alkali and water to precipitate the dye, the dye then being acidified slightly and treated with i an acid salt, said dye being completely soluble in sodium sulfide solutions and yield-- inga clear'light yellow vat. r

9. A blue sulphur dye obtained by thionating the product formed by the condensation of p-nitrosophenol and diphenylamine at a temperature below 0 (1, the dye being char acter zed by being substantially completely soluble 1n a dilute sodium sulfide solution 

